package com.Lock;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/*
* ReadWriteLock
* 独占锁（写锁）：一次只能被一个线程占有
* 共有锁（读锁）：多个线程可以同时占有
* 读读 可以共存
* 读写 不能共存
* 写写 不能共存
* */

public class ReadWriteLockTest {
    public static void main(String[] args) {
        MyCache2 myCache = new MyCache2();

        //写入操作
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.put(String.valueOf(temp),String.valueOf(temp));
            },String.valueOf(i)).start();
        }
        //读操作
        for (int i = 0; i < 5; i++) {
            final int temp = i;
            new Thread(()->{
                myCache.get(String.valueOf(temp));
            },String.valueOf(i)).start();
        }
    }
}

/*
 *自定义缓存,加锁版本
 *  */
class MyCache2{
    //
    private volatile Map<String,Object> map = new HashMap<>();
    //读写锁，更加细粒度的控制，就会有具体的读写锁控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    //存、写入的时候，只希望同时只有一个线程写
    public void put(String key,Object value){
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"写入"+key);
            map.put(key,value);
            System.out.println(Thread.currentThread().getName()+"写入ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }
    //取、读
    public void get(String key){
        readWriteLock.readLock().lock();

        try {
            System.out.println(Thread.currentThread().getName()+"读取"+key);
            map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取ok");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}
/*
*自定义缓存
*  */
class MyCache{
    //
    private volatile Map<String,Object> map = new HashMap<>();

    //存、写
    public void put(String key,Object value){
        System.out.println(Thread.currentThread().getName()+"写入"+key);
        map.put(key,value);
        System.out.println(Thread.currentThread().getName()+"写入ok");
    }
    //取、读
    public Object get(String key){
        System.out.println(Thread.currentThread().getName()+"读取"+key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName()+"读取ok");
        return o;
    }
}